This invention relates generally to a self-generating gas pressure apparatus such as an expandable pouch means positionable in a container containing a flowable material so as to provide pressure on the material so that it can be dispensed from the container, and in particular to a method for gas generation employing gas-producing chemical reactants wherein a precipitated reactant is provided in a water-dispersible suspension medium to thereby evenly disperse that reactant and enhance the maintenance of gas production and resultant pressure within the apparatus.
The use of self-generating gas pressure apparatus in general within a container from which a flowable material such as, but not limited to, a fluid is to be dispensed under pressure is well-known in the art. U.S. Pat. Nos. 4,360,131, 4,376,500, 4,478,044 and 4,513,884, for example, describe various gas-generating pressure apparatus. Typically, an expandable closed vessel such as a pouch means having a plurality of internal compartments is employed, with the compartments having interfacing barriers or individualized walls formed by seals which are rupturable under pressure. Within adjacent compartments, for example, one such compartment will contain a first chemical compound and the second compartment will contain a second chemical compound. The particular compounds are chosen from among those which react with each other to form a gas. Thus, for example, one compartment may contain citric acid, while the other compartment contains sodium bicarbonate. When these two compounds mix with each other, they react to produce carbon dioxide. To accomplish such mixing in the expandable vessel, a trigger reaction is permitted to occur which subsequently causes the rupture of the seal which interfaces between the two adjacent compartments. This results in the mixture and reaction of the two compounds to produce a gas which expands the vessel to thereby apply pressure on the material within the container in which the expandable vessel is housed. A novel self-generating pressure applying means is taught in co-pending and commonly-assigned U.S. Pat. application Ser. No. 034,900, filed Apr. 6, 1987, incorporated herein by reference.
While gas pressure generation occurs as above described and is generally adequate as long as sufficient time passes between individual dispensing procedures to thereby achieve pressure regeneration from continued chemical reaction, such generation may not be sufficiently uniform to provide optimum pressure to the material to be dispensed from the container during continued dispensing, resulting in an inconsistent or erratic flow from the container as the dispensing procedure continues. Commonly assigned U.S. Pat. No. 4,785,972, incorporated herein by reference, provides for the inclusion of a nucleating agent with the gas-producing chemical reactants to aid in uniform and rapid pressure maintenance. We now have found that by providing any such precipitated reactant in a water-dispersible suspension medium such as a gum or an algin to thereby achieve uniform suspension and dispersion thereof significantly improves pressure maintenance during the dispensing procedure. Further, by suspending precipitated and any insoluble components in the suspension, the initial filling of the expandable vessel with such suspension is much less cumbersome and is easily accomplished with automatic filling apparatus.
Accordingly, it is a primary object of the present invention to provide a self-generating gas pressure apparatus wherein gas formation occurs relatively rapidly and wherein gas pressure is relatively uniformly maintained during continued dispensing of flowable materials subjected to the gas pressure apparatus. Another object of the present invention is to provide apparatus wherein precipitated chemical compounds which react to produce gas are provided as suspensions. Yet another object of the present invention is to provide apparatus wherein resultant pressure provided by the apparatus can be pre-chosen through selected variations in quantities of reactant chemicals. These and other objects of the present invention will become apparent throughout the description thereof.